71M6515H_11 Datasheet, PDF (46/60 Pages) Teridian Semiconductor Corporation – Up to 10ppmC precision ultra-stable voltage reference Digital temperature compensation

71M6515H
A Maxim Integrated Products Brand
Energy Meter IC
DATA SHEET
JULY 2011
If higher precision is required, the host must calculate the RMS voltages from the values in the VASQSUM, VBSQSUM, and
VCSQSUM registers.
Example: The register VRMS_B reads the value 425,778,000. Assuming VMAX to be 600V, and using the
formula above, we determine the RMS voltage of phase B to:
V_RMS
=
425778000 ⋅ ^{6.8781⋅10−9600}
60
= 226.85V
WH_A (0x00), WH_B (0x01), WH_C (0x02)
These registers hold the real energy collected during the previous accumulation interval. The magnitude of the values is
determined by:
LSB = 9.4045 ⋅10^{−13 VMAX IMAX} Wh
In _ 8
Example: The register WH_A reads the value 236,675 for one accumulation interval of one second. Assuming
600V for VMAX, 208A for IMAX, and unity gain, we determine the real energy to be:
E = 236,675*600*208*9.4045*10^-13 Wh = 0.0277781Wh.
By multiplying with 3,600, we get 100Wh/h, which means the applied power is 100W.
FREQ_DELTA_T (0x11)
This register holds frequency and temperature information in two bytes each.
Bits 31-16: These bits (FREQUENCY) represent the frequency of the input signal selected with the F_SELECT bit of the
CONFIG register. One LSB is equivalent to 0.1Hz.
MAIN_EDGE_CNT (0x35)
This register holds the number of zero crossings of the input phase selected by the F_SELECT bits in the CONFIG register
detected in the previous accumulation interval. The value in MAIN_EDGE_CNT can be used by the host to correct its own
RTC or to synchronize events to the line voltage.
Registers Controlling Alarms and Thresholds
CREEP_THRSLD (0x1D)
The four bytes written to this register determine the creep threshold. Setting a creep threshold helps suppressing I2H, Wh
and VARh readings when the values of WSUM and VARSUM are determined to be below the creep threshold.
Example: The creep threshold of a meter operating with an accumulation interval of 1000ms is to be configured
to be 15mA at 240V. The meter is using a VMAX of 600V, an IMAX of 208A, and is not using the additional gain
of 8. The numerical value for the CREEP_THRSLD register is to be determined.
With 15mA, the power per phase will be 3.6W, or 0.001Wh per second. With the LSB of WSUM readings given
as 9.4045*10^-13*VMAX*IMAX [Wh], we determine the value to:
n = 0.001Wh / (9.4045*10^-13*VMAX*IMAX /In_8 Wh) = 8520.2
The rounded down value of 8520 is written to the CREEP_THRSLD register.
SAG (0x2E)
This register holds the voltage and timing threshold for sag detection.
Bits 15-0: These bits (SAG_CNT) hold the sag count. A sag condition must persist for at least SAG_CNT samples before a
sag alarm is generated. The allowed range is 1 to (2¹⁵-1), and the default is 80 (31.7ms). The time period defined by
SAG_CNT is:
T = SAG_CNT*397µs
Page: 46 of 60
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